There are different mechanisms that can be used by an ISP to communicate with a subscriber/client/user. The following list identifies the most common existing solutions:                Online methods based on the ISP access network itself                    Notification to the Web browser. intercepting the HTTP traffic and injecting a banner or input page (splash page)            Walled Garden notification, redirecting web browsing traffic to an ISP portal limiting access to only certain domains (ISP portal, antivirus download, etc.)            Instant messaging            Email            TV Screen alert            Social Media: Many social networks provide private and direct messaging to users that can be used for the notifications.                        Offline methods (analog or digital methods, without a direct relation with the connectivity of the subscriber to the ISP)                    Phone call            Postal mail            Fax            Short Message Service (SMS)                        
However, these existing notification techniques do not guarantee that notifications get to the user device and are seen by the user. More particularly:                Email. It may be possible that the email address is not used by the subscriber, that it is classified as SPAM, etc.        Phone call. For an ISP a phone call has limitations regarding suitable times and the subscriber availability.        Postal mail. Postal mail notifications may take too long.        Instant Messaging and Social Media. The lack of standardization of instant messaging solutions, and even solutions linked to network access types (mobile or fixed) increases complexity and reduces the capacity of sending a notification. Additionally, many instant messaging systems do not guarantee the delivery nor do they implement acknowledge mechanisms.        Short Message Service (SMS). As with phone calls it has limitations in terms of acceptable times, and it also lacks mechanisms to confirm that messages are read (device errors, lack of space, no forwarding SMS services).        Notification to the web browser. It is necessary that the client uses a standard web browser. Additionally, most browsers integrate complements to block publicity or for security matters, that could interfere with the notification mechanism.        Walled Garden. These solutions can affect other devices in the home/business site impacting the service (emergency calls, monitoring, business disruption)        
Moreover, some of these notification systems raise questions to the subscriber regarding the sender authenticity (email, phone calls) that reduce the notification success and require a second notification mechanism for the subscriber to validate the information. If the identity of the user device which the notification is sent to is not known, there can be problems to view the message (e.g. in small screens, incompatible browsers, etc.). Generally, the absence of intelligence and a measure of the reliability of the notification system reduce the reliability of any of these notification mechanisms themselves.
There are technologies to identify devices based on the network protocols used by them. For example:                Fingerprinting: It is a procedure that enables the identification of a network device based on its communication stack. This mechanism identifies the operating system and applications from the analysis of the information flowing through the network. As its name suggests, it is based on getting a set of behavior patterns observed in the packets it generates in order to form a “finger print” that identifies it univocally. It uses signatures based on the values of headers fields present on network packets, and how these values are filled. Fingerprinting can be either passive if it only analyzes existing traffic or active if it sends traffic to the device to force it to generate traffic. In Active Fingerprinting, packets are sent to the device and its responses analyzed. In Passive Fingerprinting, packets sent by the device are analyzed by directly listening to the local network.        
Other technologies exist that allow the remote identification of protocols and applications that are being used by a device:                DPI (Deep Packet Inspection): This technology performs a complete packet inspection beyond its header. The goal of DPI is usually looking for protocols non-compliances to identify virus, spam, intrusions, etc., as well as statistical purposes. The analysis of network traffic by DPI is centered on the data and application portion of the packets circulating through the network, beyond the protocol header.        IDS (Intrusion Detection System): It is a system that analyzes network traffic to discover attacks or intrusions indications.        Network scanners: These programs trace all the ports of a device in order to discover which are open and which applications are listening. They are also able to get the applications versions and their possible vulnerabilities. A network scanner is implemented as a computer program that identifies network nodes, protocols and services. This information can be used to identify the device.        
Additionally, many protocols include specific parameters that make it easier to identify the application type and version (User-Agent in HTML, Status Code in SMTP, etc.). There are also technologies that enable the connectivity between the ISP network and the user device located in the subscriber network:                NAT (Network Address Translation): Real time mechanism that allows the subscriber's router to translate from the subscriber's network internal IPs to the public IP assigned by the ISP to the client.        Port Forwarding: Mechanism that allows the redirection of a port in a network segment to another port. This technology makes it possible to establish a connection to a device in the internal network from the outside.        uPnP (Universal Plug and Play): Communication protocol family that allows network devices to dynamically discover the presence of other devices and establish a connection between them.        PCP (Port Control Protocol): Communication protocol, specified by RFC6887, which enables the communication with the network node that provides the NAT in order to open or redirect ports.        Web redirection: Also known as URL redirection, it is an HTTP protocol mechanism to indicate to an HTTP client to consult another URL or address when the client makes the first HTTP request. Status codes 30x implement redirection at the HTTP protocol level.        
These different solutions, enabling the identification of user devices and their communication with the ISP network, have several problems to guarantee that the notifications get to the user device.
For example, the widespread use of private addressing, specified by RFC1918 and supported by NAT technologies to provide Internet access to subscribers, requires the shared use of public addressing between the subscriber's devices and even between subscribers, and makes it difficult the exact identification of the destiny of the notification. The exhaustion of IPv4 public addressing, making ISPs share available IPv4 between subscribers by an additional NAT application, makes it even more complex the subscriber and device identification from outside the subscriber's local network.
On the other hand, fingerprinting techniques, analyzing network traffic according to the device parameters related to network protocols such as DHCP, TCP, UDP, ICMP or IP, lose effectiveness and precision when used outside the network segment (LAN) where the user device is located, such as the ISP network or the Internet. In addition, latency times are parameters that allow the categorization of Operating Systems. The reception of notifications sent from outside the subscriber's local network used in some solutions needs additional network configurations to allow the traffic to get to the device, such as adapting NAT (port forwarding, uPnP, PCP, etc) or using Firewalls in the subscriber's CPE (Customer Premises Equipment). In this situation, the notification solution gets complicated since it involves the intermediate network devices and the security policies.
Other examples of Notification user systems are described below.
U.S. 2013/0046880 A1 defines a notification mechanism to an ISP subscriber base on web redirection. However, it does not guarantee traffic assiduity or the correct adaption to any device.
U.S. Pat. No. 6,459,913 B2 describes a unified alert system to a subscriber with different notification methods. However, it is exclusively based on a subscriber generated profile, i.e., it requires the subscriber to indicate which devices will be available, and its features, as well as the priority level, according to their preferences. This priority level needs not agree with the delivery reliability given it is a subjective subscriber judgment.
U.S. Pat. No. 7,243,130 B2 describes a notification selection method deducing the user interest and location based on information from multiple probes in usage context. Nevertheless, this method does not take into account the interest of the ISP for the information to get to the subscriber with maximum guarantee, which is not always according to the subscriber interest (e.g., the subscriber might not be interested in an alert due to violations of binding agreements with the ISP). In addition, the method disclosed in U.S. Pat. No. 7,243,130 B2 requires a previous configuration and inventory, being able to deduce, based on network traffic, which devices exist, and also needs a specific probe to be configured, since the attention level information is automatically obtained from the network.
Current solutions send notifications to the user blindly, that is, without the certainty that the notification is received or seen by the subscriber. Therefore, there is a need in the state of the art for a method and system to send notifications to a device inside the IP network of an Internet Service Provider's subscriber, selecting the protocol or mechanism that provides greater guarantees of being received or perceived by the user.